Groundwater contamination by volatile organic compounds, such as gasoline, presents a serious environmental problem. Ground-water reclamation and remediation are now required by most state and/or local governments. Two major production-types of air-diffusion strippers (air-strippers) are commonly used to separate volatile organic compounds from groundwater; the stripping tower, and the sequential tray-type stripper. Both of these systems use massive volumes of air and are designed for high-flow situations where a large volume of water with relatively high concentrations of volatile organic compounds (VOC's) are present in the water.
The stripping tower is composed of a tall tower, usually 20 feet high, filled with a particular packing material designed to atomize or disperse the influent contaminated groundwater. The stripping tower inputs the contaminated ground water into the top of the tower and allows it to cascade through the packing, while a high-pressure, high-volume blower blows air past the cascading water. This causes a partial-pressure differential between the VOC-contaminated water and the "clean air" blowing past it, thereby allowing the VOC's to pass from the ground water into the by-rushing air. The resulting vapor laden with VOC's passes out through the top of the tower into the atmosphere. The water collects in the bottom of the tower and exits, by pump, through the base of the tower to a sewer drain.
The trough-type or "tray-type" sequential stripper uses similar technology as the stripping tower, however the tower is replaced by several "baffled", stacked, horizontal trays. The influent contaminated ground water enters through the top of the stack of trays, and is dispersed by the baffles. High-pressure, high-volume air is, as previously described, blown past the dispersed water, volatilizing the VOC's into a vapor which is then vented to the atmosphere. The "stripped" ground water collects in the bottom tray and exits, by pump out to a sewer drain.
Both of these systems are necessarily mounted in on-site constructed buildings for which building permits, zoning hearings, and building commission hearings are required. The addition of the equipment usually increases the owner's tax base and the installation requires a disproportionate amount of engineering and construction time.
Those concerned with these and other problems recognize the need for an improved diffused air stripping system.